1. Field of the Invention
The present invention relates to a lens driving device and, more particularly, to an electromagnetic lens driving device which includes: an electromagnetic driving module for driving a lens module to move within a casing, and a positioning structure for securing the lens module in position within the casing when power is cut off.
2. Description of the Prior Art
Please refer to FIG. 1 for an exploded perspective view of a conventional zoom lens. The conventional zoom lens uses a mechanical transmission-type focusing mechanism 9 that includes not only a multitude of transmission elements, but also a high-cost, high-precision driving element 91 (e.g., a stepper motor, ultrasonic motor, piezoelectric actuator, etc.) as a power source for driving a lens mount 93 mounted with a lens set 92. Therefore, the focusing mechanism 9 is disadvantaged by a complex mechanical structure, a complicated assembly process, a large volume, an elevated cost, significant power consumption, and consequently a high selling price.
Moreover, with continuous progress of science and technology, the traditional specialized photographic devices are improving in terms of compactness as well as image quality so as to cope with the various new products in the era of information technology. Nevertheless, the conventional stepper motor-driven zoom lens cannot be further downsized and therefore prevents the overall products from getting thinner and lighter. The electromagnetic technology is a known feasible solution to the problem described above. For instance, a voice coil motor (VCM)-based electronic feedback system can be used to monitor the shift of the coil and replace the conventional stepper motor, with a view to reducing the volume of the driving structure.
On the other hand, it is a trend nowadays to integrate products of different functions. For example, photographic functions are incorporated into mobile phones, personal digital assistants (PDAs), and laptop computers to provide enhanced image capture capabilities.
Therefore, it is a major subject of research and development in the related industry to reduce the volumes, costs, and power consumption of the various components of an integrated product that share the same power supply. It is particularly hoped that, given the same power supply capacity, the standby time and operation time of the product can be effectively increased.